1. Field of the Invention
The present invention relates to a jet-propulsion watercraft such as a personal watercraft (PWC) which ejects water rearward and planes on a water surface as the resulting reaction. More particularly, the present invention relates to a jet-propulsion watercraft comprising a device that can maintain steering capability even when the throttle is operated in the closed position and propulsion force is thereby reduced.
2. Description of the Related Art
In recent years, so-called jet-propulsion personal watercraft have been widely used in leisure, sport, rescue activities, and the like. The jet-propulsion watercraft is configured to have a water jet pump that pressurizes and accelerates water sucked from a water intake generally provided on a bottom of a hull and ejects it rearward from an outlet port. Thereby, the watercraft is propelled.
In the jet-propulsion watercraft, a steering nozzle provided behind the outlet port of the water jet pump is swung either to the right or to the left, to change the ejecting direction of the water to the right or to the left, thereby turning the watercraft to the right or to the left.
In the above-described jet-propulsion watercraft, when the throttle is moved to a substantially fully closed position and the water ejected from the water jet pump is thereby reduced, the propulsion force necessary for turning the watercraft is correspondingly reduced, and the steering capability of the watercraft is therefore reduced until the throttle is re-opened.
To solve the above-described condition, the applicant disclosed a jet-propulsion watercraft comprising a steering component to mechanically create steering capability even when the throttle is moved to a substantially fully closed position and the water ejected from the water jet pump is thereby reduced (see Japanese Patent Application No. Hei. 2000-6708).
In the jet-propulsion watercraft comprising the above-described steering component, the number of parts is increased, which results in a complex structure and increased weight. As a solution to this, there has been proposed a jet-propulsion watercraft adapted to execute the control for increasing an engine speed to thereby allow the amount of ejected water to be maintained and the steering capability to be thereby maintained (herein referred to as xe2x80x9csteering assist mode controlxe2x80x9d) when detecting a throttle-close operation of the throttle operation means and a steering operation of a steering operation means (see Japanese Patent Applications Nos. 2000-6708, and 2000-142664, and 2000-142639) assigned to the same assignee as herein.
The present invention addresses the above-described condition, and an object of the present invention is to provide a jet-propulsion watercraft which is adapted not to execute a steering assist mode control when detecting a throttle-close operation of a throttle operation means in a normal cruising state and if a signal line for detecting a steering operation of the steering operation means is disconnected.
According to the present invention, there is provided a jet-propulsion watercraft, comprising: a water jet pump that pressurizes and accelerates sucked water and ejects the water from an outlet port provided behind the water jet pump to propel the watercraft as a reaction of the ejecting water; a steering position sensor for detecting a steering operation of a steering operation means; a steering means adapted to be subjected to a steering assist mode control, when a signal indicating that the steering position sensor has detected the steering operation is received from the steering position sensor; and a control device that gives a signal to the steering position sensor and receives a signal indicating that the steering operation means is or is not steered from the steering position sensor, wherein the signal from the steering position sensor is set equal in level to the signal being given from the control device to the steering position sensor when the steering operation sensor is not steered.
In the jet-propulsion watercraft so configured, when the signal line connected to the steering position sensor is disconnected in a normal cruising state, the signal equal in level to the signal in the unsteered state is obtained from the steering position sensor. As a result, the steering assist mode control is not executed, and the normal drive cruising state can be maintained.
It is preferable that in the jet-propulsion watercraft, the signal from the steering position sensor is a HIGH level signal and the signal being given from the control device to the steering position sensor is a HIGH level signal when the steering operation means is not steered. Since no noise invades the signal, a noise-proof configuration is achieved.
In the jet-propulsion watercraft, the signal from the steering position sensor may be a LOW level signal and the signal being given from the control device to the steering position sensor may be a LOW level signal when the steering operation means is not steered.
It is preferable that in the jet-propulsion watercraft, the steering position sensor comprises a proximity switch having two proximity sensors provided on a portion of a rotational shaft of the steering operation means of the watercraft, one terminal of each of the proximity sensors is connected to the control device to allow a voltage of HIGH level to be applied to the one terminal from the control device, and the other terminal of each of the proximity sensors is electrically grounded, and when the steering operation means is steered, the proximity sensor placed on a steered side is activated to short the terminals of the proximity sensor to cause the voltage to change from HIGH level to LOW level.
In the jet-propulsion watercraft, the steering position sensor may comprise a proximity switch having two proximity sensors provided on a portion of a rotational shaft of the steering operation means of the watercraft, one terminal of each of the proximity sensors may be electrically grounded through the control device and the other terminal of each of the proximity sensors may be connected to an electric power source to allow a voltage of HIGH level to be applied to the other terminal from the electric power source, and when the steering operation means is steered, the proximity sensor placed on a steered side may be activated to short the terminals of the proximity switch to cause the voltage to change from LOW level to HIGH level.
Herein, the xe2x80x9cthrottle-close operationxe2x80x9d of the throttle operation means indicates that an operation is performed to bring the throttle toward a closed position by a predetermined amount or more.
The xe2x80x9csteering assist mode controlxe2x80x9d refers to the control for increasing the engine speed to allow the amount of ejected water to be maintained and the steering capability to be thereby maintained.
The above and further objects and features of the invention will more fully be apparent from the following detailed description of the accompanying drawings.